This invention presents an improvement in the machining art by increasing the ability of the tool operator to select and implement reasonable cutting conditions for any of a variety of materials on machine tools of differing horsepower. This invention lends itself to either manually, or numerically, controlled machining. The term "numerical control" is considered herein as encompassing the control of the operation of a machine tool in response either to directions programmed in machine language on a reuseable programming medium (e.g., a punched tape, a magnetic tape, a floppy disk) or to directions stored in the memory of a computerized numerical control machine tool.
However, regardless of whether the machining has been manually controlled or numerically controlled, the selection of the cutting conditions has historically been done in a manner, which underutilizes the capabilities of the machine tool. Thus, directions given to a machine tool operator or introduced into a numerical control program by a programmer will, depending upon the type of machining operation being performed, the material being machined, its hardness and condition and the material of the cutting tool, be based upon recommended values for speed, feed and depth of cut (DOC). These recommended values [as well as selection of cutting fluid, tool geometry (i.e., tool attitude relative to the workpiece) and general information for calculating the power required for the particular operation] are determined from handbooks, such as the Machining Data Handbook [2nd Edition, Machining Data Center, Metcut Research Associates Inc., Cincinnati, Ohio (1972)]. Such an approach has built-in rigidity and the values for speed, feed and DOC provided in this way are, unfortunately, unnecessarily conservative and can result in severe underutilization of the machine tool. The problem is compounded by the fact that many part-programmers (i.e., individuals charged with programming the machining of a part to be made) are not skilled in machining technology.
The process of this invention addresses the present problem of machine tool underutilization by enabling the iterative determination of cutting conditions for the particular machining operation (i.e., roughing or finishing) that will, while satisfying certain constraints, more fully utilize the machine tool selected. Further, this process, although it employs simple calculations for the determination of feed and DOC such that a trained operator can carry out the requisite computations and manually adjust the machine tool as appropriate, offers in the case of a numerically controlled machine tool the highly desirable option of placing the programming task in the hands of the machine tool operator.
Thus, the iterative method of this invention for selecting and implementing the cutting conditions for each of a series of machining operations to be executed in sequence to manufacture a given part can be made part of an overall computer-aided process. In such a process, once a part has been designed, the machine tool operator charged with producing the part can draw the part (or component thereof) using interactive graphics, divide the part into elements, select the sequence of machining operations, select the cutting conditions, write a numerical control program and then execute it with the machining operations being carried out by the machine tool in accordance with the program. It is expected that in addition to the advantage of better machine tool utilization, the placement of the aforementioned tasks under the control of the machine tool operator will result in increased productivity and reduced costs.